Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
  Case Tag  
Price  
Sales  
Tax %  
Raw Total  
Incl. Sales Tax  
Rounded  
to Penny  
Rounded  
to Nickel  
Rounded  
to Dime  
  Purchase #1 $236.64   10.550%   $261.6055   $261.61   $261.60   $261.60  
  Purchase #2 $175.87   12.545%   $197.9329   $197.93   $197.95   $197.90  
  Purchase #3 $77.66   13.857%   $88.4213   $88.42   $88.40   $88.40  
  Purchase #4 $96.79   8.329%   $104.8516   $104.85   $104.85   $104.90  
  Purchase #5 $112.53   13.446%   $127.6608   $127.66   $127.65   $127.70  
  Purchase #6 $150.59   8.460%   $163.3299   $163.33   $163.35   $163.30  
  Purchase #7 $227.49   6.176%   $241.5398   $241.54   $241.55   $241.50  
  7 purchase totals = $1,077.57       $1,185.3418   $1,185.34   $1,185.35   $1,185.30